I used to play League a lot and yea there's a fire hose of info you gotta learn at the beginning, especially as they continue to add new champs.

I'd say:

1. watch some kind of 'getting started video on YouTube, and search for the categories that different champs are in (e.g. support, ad carry, ap, bruiser, jungle, etc). Some of the categories overlap, because some are how the champ plays and some are their job in normal games. Google/YouTube explanations about this too.
2. If you can get those things mapped out in your head, it'll give you and idea for what kind of champ each is going to play as and against (i.e. you'll know if the person you run into is gonna be tanky and hard to kill, a glass cannon, etc).
3. Probably just stick to playing bruisers and other tanky champs for now so you don't die right away, and slowly learn as you go.

Good luck lol